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Power Hardware

Are Data Centers Finally Ready For DC Power? 462

1sockchuck writes "It's been five years since a landmark study outlined the potential benefits of DC power distribution in data centers. But adoption of DC in data centers remains limited, even as the industry aggressively pursues a wide array of other energy savings strategies. Advocates of DC distribution are hoping a new study will jump start the conversation about DC distribution, which can save energy by eliminating several wasteful AC-to-DC conversions within a data center. Meanwhile, an industry association for DC power adoption, the EMerge Alliance, has formed a new technical standards committee for data centers, and is advancing a 380-volt DC power standard. Will DC distribution ever gain momentum in data centers?"
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Are Data Centers Finally Ready For DC Power?

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  • by Animats ( 122034 ) on Wednesday November 30, 2011 @05:47PM (#38219406) Homepage

    There's no particular reason that 380 VDC distribution should help efficiency. You still need about two more levels of switching power supply before power reaches the ICs.

    Google's proposal that motherboards should need only 12VDC made more sense. Drives already run on 12VDC, and there's already a level of power conversion near the CPU to get the desired CPU voltage. The USB devices do need +5, but a 12VDC to 5VDC switching converter can handle that. And single-voltage power supplies are more efficient and simpler than multi-voltage ones.

  • why 380v? (Score:4, Interesting)

    by wierd_w ( 1375923 ) on Wednesday November 30, 2011 @05:49PM (#38219430)

    Wouldn't it make more sense to drive at 12v with an insane amperage behind it, than to drive at 380v and garantee the necessity of a voltage regulator rated for high voltages?

    I mean, the whole reason for doing away with ac current was to eliminate the rectifier and regulator circuits, which belch heat into the data center. Using 380v, which no datacenter device that I know of uses natively (well, maybe the innards of a crt, but that's actually much higher than 380v... AND a deadend tech.), seems kinda... well.... unproductive.

    Is it because of impedence problems or something?

  • by mlts ( 1038732 ) * on Wednesday November 30, 2011 @05:58PM (#38219588)

    If one has worked in a telco, we already have a standard, and that is 48VDC. This is the domain of the Sun Netras of yore.

    If I were to recommend a voltage, why not plain old 12VDC? Yes, the amps have to be high, but we already have a connector for this (beats wiring up things by hand and throwing a breaker), and it is not hard to find off the shelf hardware to support this, be it batteries, power distribution units, inverters/converters, solar panels with MPPT controllers, and so on. We have two large markets (RV/marine) that are dedicated to 12VDC.

    Why not just use an established standard? 12VDC works and has a lot of support, or if a higher voltage is needed, then 48VDC.

    384VDC just seems to be asking for trouble. It would require yet another separate connector that can't be plugged into 120VAC or 240VAC, generators would have to have an adapter for it. It would require a complete retooling to get to that standard.

    Making another voltage level is throwing the baby out with the bathwater. Why not just go with an established DC voltage level?

    Take 12VDC. Most generators, from the expensive inverters by Honda or Yamaha can generate that, as well as the construction grade open-framed ones.

  • by LehiNephi ( 695428 ) on Wednesday November 30, 2011 @05:58PM (#38219602) Journal
    I do/have done both (run electrical and understand the implications), and GP has a point. When I think of the things in our house that *must* run on AC, it's only our fridge, freezer, and HVAC. Everything else in the house either converts it to DC or could run quite happily on DC. For certain you'd want to have a different kind of plug for DC devices, but even that would give us an opportunity to 1) standardize on one global plug standard, at least for DC, and 2) allow us to design a small, rugged, safe type of plug.

    Or is there some implication that I'm missing, and that you decided not to point out, in favor of flaming GP?
  • by vlm ( 69642 ) on Wednesday November 30, 2011 @06:05PM (#38219724)

    For certain you'd want to have a different kind of plug for DC devices, but even that would give us an opportunity to 1) standardize on one global plug standard, at least for DC, and 2) allow us to design a small, rugged, safe type of plug.

    Aka the famous (in some circles) Anderson Power Pole. Go ask a ham radio guy.

    The thing I love about in house DC distribution, which I have in my house, is it forces at least a token effect at "green power reduction". Suddenly given the choice of a 12 volt 6 watt LED fed by $2 of small gauge wire vs something resembling welding cable wire to run a 200 watt halogen, you make the ecologically correct choice.

    I used to use cast off surplus 200 watt desktops for my mythtv frontends. Unholy pain to run on 12 V. Now I use 5 watt Zotac boxes. Good for everyone in every way.

  • by vlm ( 69642 ) on Wednesday November 30, 2011 @06:11PM (#38219830)

    4) Done right with a positive ground system, leads to less corrosion problems with outside plant. Admittedly "inside" the data center, if you're got corrosion, you're doin it wrong.

    5) Less AC hum. We had some microwave site to site short hop gear back in ye olde NTSC days that could only be run off battery without 60 hz interference bars on the screen. Not technologically relevant anymore, but the point remains that DC is always going to be cleaner than AC.

    6) Better lightning protection. I'm sure its happened, but I've never heard of losing a telco DC bus. Big conductors, giant batteries across them, lightning is just not an issue anymore at the power level (still need to ground feedlines / waveguide / whatever you've got at home like that)

    7) dump most of the power conversion heat in the battery room where its all built to handle high temp and no one visits (other than occasional battery maint). Cheaper cooling in the data center, data center is somewhat more habitable, etc.

  • by Anonymous Coward on Wednesday November 30, 2011 @06:17PM (#38219938)

    It's not only the radiation that makes AC less efficent. It is also how you can build conductors.

    If you built just a simple very long cylinder out of copper, it is the perfect conductor for DC. For AC only the border is used, as the electric field presses electrons there. So with AC you have to use complex cables working around this, while with DC you get better behaviour with a simpler and less expensive design.

    You won't get that for small voltages. But for the big power lines going long distances, this is significant. (And the reason why newer lines are DC nowadays, in the rare cases where there are newer lines).

  • by hpa ( 7948 ) on Wednesday November 30, 2011 @06:21PM (#38220014) Homepage
    USB is designed to enable inexpensive devices. 5 V is so that when cable losses are counted in, you can use a LDO linear regulator to obtain 3.3 V (Vcc) without excessive losses. 12 V would require a switching regulator.
  • by garlicbready ( 846542 ) on Wednesday November 30, 2011 @07:30PM (#38220788)

    When it comes to high voltages one of the other advantages AC has is safety
    with High Voltage DC the muscles in your hand would tend to grip / contract or hold onto a conductor
    AC on the other-hand just tends to throw you off as it's alternating back and forth at 50 or 60 times a second
    The longer your in contact the more chance you have of suffering burns, or your heart stopping

    I'd guess 12V / 24V is probably the best, as it's low enough not to be a safety risk (think car battery)
    and at the same time most PC Hardware tends to run on a combination of 12V / 5V anyway (converting from 12 to 5 is trivial)
    Having an AC to DC conversion on the side of the wall then running a cable to each rack perhaps in a ring configuration might be the way to go
    probably depends on the amount / size / thickness of cabling you can fit in to each rack / under the flooring

    When they talk about losses, usually it's over long distance over a few miles or between substations
    although I have heard that you can get losses of a few volts of AC between opposite sides of a hanger for example
    but that's likely to be less controlled / more dirty than regulated DC within a Datacenter
    Also with 12V there may be a lot less cost in terms of replacing the server PSU's as it's already closer to what you already need

    Of course the most important thing is that we'd need some form of new standard plug
    perhaps a different colour and some extra pins for future expansion
    perhaps google should ask apple, I hear they're good with plug design :)

  • by zerofoo ( 262795 ) on Wednesday November 30, 2011 @09:57PM (#38222000)

    My 2008 VW GTI has an electric assist rack, and it is one of the best systems I've ever felt in terms of feedback and heft. I've also driven overboosted hydraulic systems that feel like mush.

    Electric assist steering can be done well, and hydraulics can be done poorly. The technology isn't to blame, it's the engineering that matters.

Perfection is acheived only on the point of collapse. - C. N. Parkinson